WO1996010857A1 - Current differential protection arrangement - Google Patents
Current differential protection arrangement Download PDFInfo
- Publication number
- WO1996010857A1 WO1996010857A1 PCT/DE1995/001372 DE9501372W WO9610857A1 WO 1996010857 A1 WO1996010857 A1 WO 1996010857A1 DE 9501372 W DE9501372 W DE 9501372W WO 9610857 A1 WO9610857 A1 WO 9610857A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- current
- differential
- current values
- stabilization
- blocking
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
- H02H3/283—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus and taking into account saturation of current transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
- H02H7/0455—Differential protection of transformers taking into account saturation of current transformers
Definitions
- the invention relates to a current differential protection arrangement for an electrical power supply unit with a measured value preprocessing device in which differential current values are continuously formed from currents detected at the ends of the power supply unit in the event of a fault, and with an evaluation device in which, based on a predetermined dependency of the differential current on the stabilizing current (Response characteristic) is checked whether the respectively formed differential and stabilizing current values describe a point on one side of the response characteristic (blocking area) or a point on the other side of the response line (triggering area), the evaluation device with regard to the formation of the Barrier area is designed so that an additional stabilization area is present in the lock area to achieve additional stabilization, which by a below one at a predetermined Stabilizing current value beginning and lying in the predetermined manner linearly with the stabilizing current increasing characteristic curve section of the barrier area is defined.
- a current differential protection arrangement of this type is obviously used in the form of the Siemens 7UT51 V2.1 digital differential protection and its essential structure is described in the associated equipment manual with order number C 73000-G 1100-C77-7.
- the currents I 1 and I 2 are detected at ends 1 and 2 of an electrical power supply unit 3, which is, for example, a motor, a transformer or one monitoring line section of an electrical Energy supply network can act.
- an electrical power supply unit 3 which is, for example, a motor, a transformer or one monitoring line section of an electrical Energy supply network can act.
- the positive current direction is, for example, a motor, a transformer or one monitoring line section of an electrical Energy supply network.
- stabilization current values ISTAB assigned to the differential current values are generated in accordance with the following relationship (2):
- I STAB II 1
- the differential current values and the stabilizing current values are formed in a measured value preprocessing device, which is not shown in detail in FIG. 1.
- the respective switching group is also taken into account in the measured value preprocessing device - as can be seen in the above-mentioned manual on page 27 - and the zero currents are also eliminated.
- an evaluation device downstream of the measured value preprocessing device evaluates the respectively formed differential and stabilizing current values in such a way that it is checked on the basis of a predetermined dependency of the differential current on the stabilizing current (response characteristic curve) whether the respectively formed current values have a point on one side the response characteristic, i.e. in the restricted area, or describe a point on the other side of the response characteristic, i.e. in the triggering area. If there are current values that are in the triggering area, then the
- an additional stabilization is used in the obviously previously used device, with which stabilization when the transformers required for current detection are saturated, e.g. converters 5 and 6 according to FIG. 1 are to be reached; An internal fault can be simulated by converter saturation.
- the evaluation device therefore defines an additional stabilization area in the blocked area, which represents a section of the blocked area. This section is characterized by a value that starts below a predetermined stabilization value and increases linearly with the stabilization current in a predetermined manner
- Boundary section of the barrier area defined.
- the described structure of the known current differential protection arrangement ensures that, despite the inevitable transformer saturation, a trip command is not given in the event of an external fault with respect to the electrical power supply unit to be monitored; this is made possible by the fact that the converters still correctly transmit the currents for a few milliseconds and only then saturate while falsifying the current values. If an external fault is detected before saturation, then a blocking occurs in the known differential protection arrangement carried out, which prevents a trip command in the event of a saturation of an internal fault.
- a current differential protection arrangement for a transformer is also known (essay by H.-J. Herrmann and U.
- the invention is based on the object of developing the known current differential protection arrangement described at the outset in such a way that even in the event of an internal fault following an external fault with converter saturation, this internal fault can be detected quickly and reliably and a corresponding trigger command can be given.
- the evaluation device in a stabilization circuit contains a test arrangement which examines the differential and stabilization current values formed in each case to determine whether they describe a point in the additional stabilization range, and those for a first determined point in the Additional stabilization area emits a blocking signal after the occurrence of an error;
- a blocking device with an associated reset device is arranged downstream of the test arrangement in such a way that, on the one hand, the blocking device is triggered by the blocking signal is activated and, on the other hand, at a first determined point outside the additional stabilization area in the course of the same fault, a timer in the reset device is started with a predetermined time delay, which is connected on the output side to a reset input of the blocking device and resets the blocking device after the predetermined time delay.
- the main advantage of the current differential protection arrangement according to the invention is that even in the event of an internal fault immediately following an external fault in the electrical power supply unit to be monitored, a trigger command is correctly generated by checking the differential and stabilizing current values with regard to the points described by them as to whether they are in the additional stabilization range. If a point in the additional stabilization range is determined for the first time after the occurrence of an error with the differential and stabilization current values, a blocking signal for activating the
- Blocking device generated. Since the stabilization and differential current values only describe a point in the additional stabilization range in the case of an external fault, it has already been established that there is an external fault and the blocking device can be blocked in order to prevent the current transformer from becoming saturated without affecting the Tripping behavior of the invention
- the timing element ensures with a predetermined time delay that the blocking device is blocked during the converter saturation and therefore cannot give off a trigger signal.
- the current differential protection arrangement according to the invention, there is therefore no blocking in the event of an internal fault immediately following an external fault Time of the detection of an external error made for a predetermined time, but only from a time dependent on the respective conditions for a predetermined time.
- Reset device a monitoring device is present, which is acted upon on the input side with the differential and stabilization current values and is connected on the output side to a time stage with a predetermined time delay; the monitoring device has one on the input side
- Quotient generator which forms the quotient from the respective differential and stabilization current values; in the monitoring device the quotient is one
- This embodiment of the current differential protection arrangement according to the invention has the advantage that the blocking device is unlocked again when the quotient of the respective differential current value and the respective associated stabilizing current value exceeds a certain limit value and the time period predetermined by the time stage has expired is, so that it is also ensured here that after an external error occurs first
- the reset device contains a monitoring arrangement acted upon with the differential and stabilization current values, on the input side contains an arrangement for forming the quotient from the differential and stabilizing current values;
- the arrangement for forming the quotient is followed by a difference generator, which forms the difference between the quotients, which are in each case successively formed, from the difference and stabilization current values, and the difference generator is followed by a threshold value detection arrangement in which the difference, which is formed
- the monitoring arrangement is connected to the blocking device via a counting device for the first control signal, which outputs a reset signal for the blocking device at a predetermined counter reading.
- This embodiment has the significant advantage that in the case of internal errors with relatively low currents following an external error with converter saturation, a rapid and reliable detection of the internal error is also possible because the blocking device then already - before the timing element downstream of the test arrangement has expired - can be activated when the counting device has issued a reset signal for the blocking device. Since the counter device is acted upon by the first control signal, it can at the earliest issue a reset signal after the converter saturation has subsided.
- the timing element, the timing stage and the counting device are advantageously connected via a logic element to the reset input of the blocking device.
- the measured value preprocessing device in the current differential protection arrangement according to the invention contains a calculation unit in which measured values proportional to the effective values are formed from the recorded currents, with which the differential and stabilizing current values are obtained. Quantities proportional to the effective value can be formed, for example, by filtering or rectification.
- FIG. 2 is a block diagram of an embodiment of the current differential protection arrangement according to the invention, in
- FIG. 3 shows part of an evaluation device according to FIG.
- Test arrangement and reset device in Figure 4 a diagram with response characteristic and boundary line of the additional stabilization range, in
- FIG. 6 shows several diagrams to explain the mode of operation of the current differential protection arrangement according to the invention in the event of an internal fault and in
- FIG. 7 shows several diagrams to illustrate the behavior of the current differential protection arrangement according to the invention in the event of an internal fault following an external fault.
- the block diagram of the current differential protection arrangement according to the invention shown in FIG. 2 contains a measured value preprocessing device 10 which is supplied with the detected current I 1 at its inputs 11 and 12 (compare also FIG. 1) and with the current I2 at its inputs 13 and 14.
- the measured value preprocessing device 10 is provided on the input side with a measured value detection block 15, in which differential currents and stabilizing currents are formed in a known manner.
- a switching group adaptation is also carried out in the measured value acquisition block 15; the amount is also adjusted here.
- the measured value preprocessing takes place in the measured value processing block 15 after analog-digital conversion in a digital manner, so that corresponding differential current values IDIFF are fed to a calculation unit 17 via a data bus 16.
- This calculation unit 17 receives, via a further data bus 18 from the measured value processing block 15, stabilization current values ISTAB proportional to the stabilization current in digital form.
- I DIFFe and I STABe formed, each of which is fed to an evaluation device 21 via a further data bus 19 and 20.
- the evaluation device 21 contains a release device 22, a stabilization circuit 23 for harmonic harmonics, a quick release device 24 and a further stabilization circuit 25.
- the measured value preprocessing device 10 also contains a filter unit 26, which is also connected to the data bus 16 on the input side and contains the fundamental oscillation and the second and filters out fifth harmonics. On the output side is
- Filter unit 26 is connected to the stabilization circuit 23 and the quick release device 24 via an additional data bus 27.
- the quick release device 24 is located
- the output signals of the individual units 22 to 25 of the evaluation device 21 are connected to a logic circuit 28 which, when suitably acted upon, emits a trip command to circuit breakers (not shown) assigned to the electrical power supply unit to be monitored.
- FIG. 3 shows the further stabilization circuit 25 of the evaluation device 21 according to FIG. 2 in detail.
- the further stabilization circuit 25 has a test arrangement 30 which is connected to the data buses 19 and 20 on the input side
- differential current values I DIFFe and stabilizing current values I STABe are applied to these data buses.
- differential current values and stabilization current values which are in each case associated with one another, are checked to determine whether they each define points which lie in an additional stabilization area 31 (see FIG. 4).
- the additional stabilization area 31 according to FIG. 4 forms part of a
- Blocking area 33 which by a response characteristic 34 is delimited from a triggering area 35.
- Figure 4 thus shows that with each assigned to each other
- a trigger command is not given, whereas a trigger command is issued when mutually assigned differential and stabilization current values describe a point in the trigger region 35.
- the test arrangement 30 checks whether, after an error has occurred, differential and stabilization current values I DIFFe and I STABe , which fall into the additional stabilization area 31, result; in particular, it is checked when a first point formed by the current values falls in the additional stabilization area 31. If, for example, there is an external error to which FIG. 5 refers, then such a point is determined after a few milliseconds at time TI, as shown in diagram B in FIG. 5, in which the difference current IDIFF as a function of the stabilizing current ISTAB is shown. The test arrangement 30 then outputs a blocking signal in the form of a "1" signal at its output
- Blocking device 37 is blocked from time T1. If the test arrangement 30 subsequently determines that the curve 38 in diagram B of FIG. 5, which results from successive points of the current values, moves out of the additional stabilization area 31, then a "0" signal is generated at this time T2 Via an inverter 39 (compare FIG. 3), a downstream time stage 40 starts in a reset device 41 for a predetermined time period e. As diagram B in FIG. 5 also shows, curve 38 cuts through response characteristic 34 after about 10 ms, whereupon trigger device 22 of evaluation device 21 (see FIG. 2) emits a signal on the output side.
- this signal must not lead to a trigger command because, in the present case, an external fault with regard to the electrical power supply unit to be monitored has been assumed, the exceeding of the response characteristic 34 can therefore only be attributed to saturation phenomena of the current transformers involved.
- the output signal of the trigger device 22 is shown in diagram E in FIG.
- the curve 38 subsequently also takes on lower values again, in order finally to cross the boundary line 32 of the additional stabilization region 31 at the time T3.
- the blocking device 37 is blocked again; the blocking device 37 was namely deactivated again at the time T4 after the time stage 40 had expired.
- FIG. 5 shows in its diagram A the course of the currents I 1 and... Detected at the ends of the electrical power supply unit to be monitored 12 is reproduced as a function of time in periods of the network, the curve shown in broken lines in this diagram representing the differential current I DIFF . It can be clearly seen that within the first two
- Periods of the differential current assume relatively large values, which is mainly due to transformer saturation in the assumed external fault.
- the diagram H in FIG. 5 shows the time course of the trigger command and in dependence on the time in periods indicates that a trip command has not been generated for the assumed external fault despite converter saturation.
- the reset device 41 according to FIG. 3 is not only connected to the test arrangement 30 with respect to the timing element 40, but is also connected to the buses 19 and 20 with a monitoring device 42, which thus also applies the differential current values I DIFFe and stabilization current values I STABe is.
- the monitoring device 42 is provided on the input side with a quotient generator 43, in which the quotient Q is formed from the respective differential current value I DIFFe and the respective associated stabilizing current value I STABe .
- the quotient generator 43 is followed by a threshold value detection device 44 which, when the value of the value exceeds a threshold value b
- Quotient Q emits a "1" signal, one of which
- subordinate time step 45 is set.
- the time stage 45 is connected to an OR gate 46
- Reset input 47 of the blocking device 37 connected; Incidentally, the output of the timing element 40 is also connected to the reset input 47 of the blocking device 37 via the OR gate 46. If the quotient Q is detected by the threshold value detection device 44, which is smaller than the threshold value b, then a "0" signal is generated which the time stage 45 uses an upstream inverter
- FIG. 5 flashed back to diagram C.
- the quotient Q from the respective differential current I DIFFe and the associated stabilization current I STABe is plotted and the threshold value b is plotted. It can be seen from diagram C that in the case shown the quotient Q does not exceed the threshold value b, so that the monitoring device 42 outputs a "0"signal; the time step 45 is therefore not set. The blocking device 37 is therefore not influenced by the monitoring device 42 in this case.
- FIG. 3 shows that the resetting device 41 is provided with a monitoring arrangement 48, which is also supplied with differential current values I DIFFe and stabilizing current values I STABe on the input side via the data buses 19 and 20.
- the monitoring arrangement 48 is in turn provided on the input side with an arrangement for forming the quotient 49, which is followed by a differential generator 50.
- this difference generator 50 the difference of successively generated quotients Q is formed in each case, and it is checked in a downstream threshold value detection arrangement 51 whether the difference of the quotients is greater than a threshold value c or less than a further threshold value d is. If there is a difference of the quotients Q with a threshold value greater than c, then a flip-flop 52 is used
- Counting device 53 incremented; If a difference of the quotients Q is determined to be smaller than the threshold value d, then the flip-flop 52 is reset again, ie the counting device 53 is no longer counted up.
- the counting device can be set differently with respect to a counter limit level g; at a limit level g of
- Counting device emitted a signal to the OR gate 46, whereupon the blocking device 37 is reset.
- the counter 53 is reset by the OR gate 46.
- Diagram D shows the lower threshold value d, whereupon the flip-flop 52 is reset; counting device 53 is therefore not counted further. If the counter is set to a counter limit of "2", there is no signal at its output to the OR gate 46, and the
- Blocking device 37 is not reset; so it remains activated.
- FIG. 6 shows diagrams A to H similar to FIG. 5, but the course of the variables described in detail above for the case of an internal error with saturation.
- the course of the currents I 1 and I 2 is again shown in the diagram A over time in periods, the dashed curve in turn representing the differential current I DI FF .
- Diagram B in FIG. 6 shows that with the assumed internal error, curve 60 formed by the individual successive points from differential and stabilizing current values I DIFFe and I STABe differs from curve 38 according to diagram B in FIG 5 does not intersect the additional stabilization area 31, but extends far above the response characteristic 34.
- the trigger circuit 22 (see FIG. 2) responds at a time T5 after the occurrence of the error, which is due to the reaction time.
- a blocking of the blocking device 37 (see FIG. 3) does not take place, as can clearly be seen in the diagram F in FIG.
- a trigger command is thus given via the logic circuit 28 according to FIG. 2 at time T5 without further delay.
- Reset device 41 has no influence on that
- FIG. 7 shows the relationships as they result from an internal error following an external error.
- the diagram A in FIG. 7 again shows the course of the currents I 1 and I 2 as a function of time in periods and the differential current I DIFF that results in each case.
- Diagram B shows that, at time T10, curve 61 formed by the individual points of the differential and stabilization current values acquired one after the other enters additional stabilization current region 31, whereupon test arrangement 30 (see FIG. 3), via its output 36, blocks device 37 is activated immediately.
- the curve 61 intersects the boundary line 32 of the additional stabilization area 31, whereupon the test arrangement 30 generates a "0" signal at its output 36 which, after inverting, causes the timer 40 to start up for the predetermined time delay e.
- Curve 61 then intersects response characteristic curve 34 at time T12 due to converter saturation, whereupon a "1" signal is generated by trigger circuit 22 (cf. FIG. 2) of evaluation device 21, as can be seen in diagram E in FIG .
- curve 61 again cuts response characteristic 34 (converter saturation has decayed), whereupon trigger circuit 22 returns to the "0" state.
- the converter saturation that occurred between times T12 and T13 has no influence on the tripping behavior of the differential protection arrangement because the blocking device 37 was activated in the time interval between T12 and T13.
- Diagram C of FIG. 7 - steeper and if it reaches the threshold value b comparatively quickly, the triggering is effected by the blocking device 37 being deactivated after the time delay f has expired.
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- Emergency Protection Circuit Devices (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP95933317A EP0783788B1 (en) | 1994-09-30 | 1995-09-26 | Current differential protection arrangement |
US08/809,765 US5808844A (en) | 1994-09-30 | 1995-09-26 | Current differential protection arrangement |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DEP4436254.4 | 1994-09-30 | ||
DE4436254A DE4436254C1 (en) | 1994-09-30 | 1994-09-30 | Differential current protection device for electrical energy supply |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996010857A1 true WO1996010857A1 (en) | 1996-04-11 |
Family
ID=6530448
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DE1995/001372 WO1996010857A1 (en) | 1994-09-30 | 1995-09-26 | Current differential protection arrangement |
Country Status (4)
Country | Link |
---|---|
US (1) | US5808844A (en) |
EP (1) | EP0783788B1 (en) |
DE (1) | DE4436254C1 (en) |
WO (1) | WO1996010857A1 (en) |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7050456B1 (en) * | 1998-12-04 | 2006-05-23 | Tekelec | Methods and systems for communicating signaling system 7 (SS7) user part messages among SS7 signaling points (SPs) and internet protocol (IP) nodes using signal transfer points (STPs) |
US6341055B1 (en) * | 1999-10-15 | 2002-01-22 | Schweitzer Engineering Laboratories, Inc. | Restraint-type differential relay |
US6625551B1 (en) * | 2000-06-09 | 2003-09-23 | Siemens Aktiengesellschaft | Fault current and differential current detection system capable of preventing spurious triggering of a protection system due to transient interference pulses |
DE10106279A1 (en) | 2001-02-05 | 2002-08-29 | Siemens Ag | Method for generating a trigger signal according to the current differential protection principle and current differential protection arrangement |
CN100365898C (en) * | 2003-07-16 | 2008-01-30 | 国电南京自动化股份有限公司 | Anti-current mutual inductor saturated conventional difference current trajectory scanning and discrimination method |
US7983014B2 (en) * | 2006-07-19 | 2011-07-19 | Hitoshi Kijima | Disconnector and overvoltage protection device |
WO2008025309A1 (en) | 2006-08-31 | 2008-03-06 | Siemens Aktiengesellschaft | Differential protection method and differential protection unit |
RU2444829C1 (en) * | 2010-09-10 | 2012-03-10 | Общество с ограниченной ответственностью "Исследовательский центр "Бреслер" | Method to detect complicated damage of electric system |
CN102879671B (en) * | 2012-09-17 | 2015-01-21 | 华北电力大学 | Method for judging inrush current locking of equivalent instantaneous inductance for protection of extra-high voltage regulating transformer |
EP2722954A1 (en) * | 2012-10-16 | 2014-04-23 | ABB Technology AG | Method of operate Is-limiters in ring systems |
CN104798276B (en) * | 2012-11-26 | 2017-09-01 | 西门子公司 | Differential protecting method and the protection equipment for performing differential protecting method |
ES2412604B2 (en) * | 2012-12-20 | 2014-03-27 | Universidad Politécnica de Madrid | Differential protection blocking method to avoid unwanted trips based on joint phase monitoring |
US20170138996A1 (en) * | 2014-03-28 | 2017-05-18 | Siemens Aktiengesellschaft | Differential protection method and differential protection device |
US10782360B2 (en) * | 2015-05-04 | 2020-09-22 | General Electric Company | Systems and methods for monitoring and diagnosing transformer health |
RU2642506C1 (en) * | 2016-09-22 | 2018-01-25 | Общество с ограниченной ответственностью "Релематика" | Method for recognition of faulty phases of electric transmission lines in open-phase earth short-circuit |
CN113922329B (en) * | 2021-08-31 | 2024-03-15 | 科华数据股份有限公司 | Power supply circuit adjusting method and device and power supply system |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0348673A1 (en) * | 1988-06-28 | 1990-01-03 | Asea Brown Boveri Ag | Process for the protection of an electrical protection object |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1400054A (en) * | 1971-09-24 | 1975-07-16 | Unisearch Ltd | Protection of transformers |
US4204237A (en) * | 1978-11-30 | 1980-05-20 | Gould Inc. | Solid state transformer differential relay |
JP2510498B2 (en) * | 1985-10-14 | 1996-06-26 | 東京電力株式会社 | Transformer failure detection method and device |
-
1994
- 1994-09-30 DE DE4436254A patent/DE4436254C1/en not_active Expired - Fee Related
-
1995
- 1995-09-26 US US08/809,765 patent/US5808844A/en not_active Expired - Fee Related
- 1995-09-26 EP EP95933317A patent/EP0783788B1/en not_active Expired - Lifetime
- 1995-09-26 WO PCT/DE1995/001372 patent/WO1996010857A1/en active IP Right Grant
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0348673A1 (en) * | 1988-06-28 | 1990-01-03 | Asea Brown Boveri Ag | Process for the protection of an electrical protection object |
Also Published As
Publication number | Publication date |
---|---|
EP0783788B1 (en) | 1998-07-08 |
DE4436254C1 (en) | 1996-02-01 |
EP0783788A1 (en) | 1997-07-16 |
US5808844A (en) | 1998-09-15 |
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